Observational Constraints on The Evolution of Dust in ...

More documents

Recommendations

Info

142 From Protoplanetary Disks to Planetary Systems the species formed, contrary to the models assumptions. For the regions presented in this study, it can be seen in Table 6.2 for mean cluster values and in Tables A.1 and A.2 for individual objects that the results derived from this study generally follow those of Bouwman et al. (2008), with more enstatite in the warm component and, to a lesser extent, more forsterite in the cold component. The right panel of Figure 6.7 illustrates this for the cumulative fraction of the forsterite over enstatite ratios for individuals disks. However, this trend is not very significant given the uncertainties. 6.4.4 The Silicate Strength-Shape Relation A correlation between the shape and the strength of the 10 µm silicate feature from disks has been discussed extensively in the literature (van Boekel et al. 2003; Kessler- Silacci et al. 2006; Olofsson et al. 2009; Pascucci et al. 2009; Oliveira et al. 2010; Olofsson et al. 2010). Synthetic 10 µm features generated for different grain sizes and compositions have been shown to fit well with observations, yielding grain size as the important parameter responsible for such a relationship. The degree of crystallinity of the dust also plays a role on the shape of this feature. However, as clearly shown for EX Lup (Ábrahám et al. 2009), and supported by models (Min et al. 2008; Olofsson et al. 2009), an increase in crystallinity fraction does not change the strength of the feature, even though its shape does change. Crystallinity is then understood as responsible for the scatter in the strength-shape relationship, and not the relationship itself. As a result, the strength and shape of the 10 µm silicate feature yield the typical size of the grains in the upper layers of the disk at a few AU from the star (Kessler-Silacci et al. 2007). The top panel of Figure 6.9 shows the results for Serpens, Taurus, Upper Sco and η Cha. The bottom panel presents the median values per region, indicating the 15 – 85 percentile ranges of the distributions. Overlaid are the models of Olofsson et al. (2009) for different grain sizes (0.1 – 6.0 µm) generated for amorphous silicates of olivine and pyroxene stoichiometry, and a 50:50 mixture. The difference in mean ages does not correspond to a significant difference in mean grain sizes between the different regions. With the mean grain sizes derived from the spectral decomposition, it is possible to further explore the validity of using the strength of the 10 µm silicate feature to trace the sizes of grains in the surfaces of disks. The left panel of Figure 6.10 shows the correlation between 〈a warm 〉 and S 10µm peak of -0.29, P = 0.01 supports the effectiveness of S 10µm peak smaller values of S 10µm peak implying larger grain sizes. for all 4 samples. The Kendall τ coefficient as a proxy for grain sizes, with On the other hand, it is also possible to test how the degree of crystallinity can influence the strength of the 10 µm silicate feature. The lack of correlation between C warm and S 10µm peak (τ = -0.07, P = 0.14), shown in the right panel of Figure 6.10 for all samples, supports that the degree of crystallinity is not the dominant parameter setting the strength of the 10 µm silicate feature. These results argue against the results of Sargent et al. (2009) that find a high crystallinity fraction and small grains
Evolution of Dust in Protoplanetary Disks 143 Figure 6.9 – Top: The ratio of normalized fluxes at 11.3 to 9.8 µm (S 11.3 /S 9.8 ) is plotted against the peak at 10 µm (S 10µm peak ) for Serpens (black dots), Taurus (gray squares), Upper Scorpius (gray stars), η Chamaeleontis (gray triangles). Bottom: Squares show the median values and crosses indicate the 15 – 85 percentile ranges of the distributions (top panel). Colored curves are derived from theoretical opacities for different mixtures by Olofsson et al. (2009). The open circles correspond to different grain sizes, from left to right 6.25, 5.2, 4.3, 3.25, 2.7, 2.0, 1.5, 1.25, 1.0 and 0.1 µm. (A color version of this figure is available in the online journal) Figure 6.10 – Left panel: Strength of the 10 µm silicate feature (S 10µm peak ) versus the mass-averaged mean grain size for the warm component. Right panel: Strength of the 10 µm silicate feature versus crystalline fraction for the warm component. The best fit relationships are shown for reference. Symbols as in Figure 6.9. (A color version of this figure is available in the online journal) fitting low strengths of the 10 µm silicate feature. Although it may be possible to fit a few spectra with a certain prescription, a good model should be able to explain
Page 1:
Observational <str
Page 4 and 5:
Promotiecommissie Promotor: Co-Prom
Page 6 and 7:
Cover Artwork: Roderik Overzier
Page 8 and 9:
viii Chapter 3. YSOs in the Lupus M
Page 10 and 11:
x Publications 217 Acknowledgments
Page 12 and 13:
2 Introduction planets may eventual
Page 14 and 15:
4 Introduction Figure 1.1 - Illustr
Page 16 and 17:
6 Introduction 1.3.1.1 Disk Observa
Page 18 and 19:
8 Introduction 1.3.1.3 Processes Af
Page 20 and 21:
10 Introduction of them (e.g., β P
Page 22 and 23:
12 Introduction responsible for dis
Page 24 and 25:
14 Introduction Figure 1.4 - Eviden
Page 26 and 27:
16 Introduction stars (due to spect
Page 28 and 29:
18 Introduction the potential to ch
Page 30 and 31:
20 Introduction Gorti, U., Dullemon
Page 33 and 34:
2 Optical Characterization of a New
Page 35 and 36:
Evolution of Dust in Protoplanetary
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59:
Page 62 and 63:
52 YSOs in the Lupus Molecular Clou
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 87 and 88:
4 A Spitzer Survey of Protoplanetar
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102: Evolution of Dust in Protoplanetary
Page 121 and 122: A. Background Sources 111 Table 4.3
Page 123 and 124: A. Background Sources 113 Figure A.
Page 125: A. Background Sources 115 Figure A.
Page 128 and 129: 118 Discovery of a Dusty Planetary
Page 138 and 139: 128 From Protoplanetary Disks to Pl
Page 176 and 177: 166 Spectral Energy Distributions o
Page 201 and 202: Nederlandse Samenvatting Inleiding
Page 203 and 204:
193 Figuur 1 - Het ontstaan van een
Page 205 and 206:
195 kunnen worden om de verschillen
Page 207 and 208:
197 Figuur 3 - Het planeetvormingsp
Page 209 and 210:
199 parameter is. Na 6 tot 8 miljoe
Page 211 and 212:
201 van de X-shooter in het ultravi
Page 213 and 214:
Resumo em Português Restrições O
Page 215 and 216:
205 Figura 1 - Ilustração do cen
Page 217 and 218:
207 Figura 2 - O Telescópio Espaci
Page 219 and 220:
209 interagem gravitacionalmente, a
Page 221 and 222:
211 e discos são conectados, é ba
Page 223:
213 uma correta separação entre a
Page 226 and 227:
216 Curriculum Vitæ omy Center (ES
Page 228 and 229:
218 Publications 8. c2d Spitzer-IRS
Page 230 and 231:
220 Thesis Acknowledgments Liesbeth
show all

Observational Constraints on The Evolution of Dust in ...

Create successful ePaper yourself

Delete template?

Save as template?